This invention relates to loudspeaker suspensions, including surrounds and spiders.
Referring to FIG. 1, a typical loudspeaker 14 includes a stiff cone 15 connected to a voice coil 20 at the apex of the cone. The loudspeaker can include a dust cap 23 attached to the cone. The voice coil 20 interacts with the magnetic circuit formed from permanent magnet 25, back plate/pole piece structure 30, and top plate 21. When the voice coil is driven by an audio signal, the cone vibrates axially to produce sound.
An outer edge 40 of the cone is attached to a rigid basket 45 along an annular mounting flange 47 by suspension element 50, typically referred to as a surround. The voice coil 20 and/or apex of cone 15 may be attached to another section of the rigid basket 45 by second suspension element 35, typically referred to as a spider. The surround 50 is often made from a flexible material such as fabric, that allows the cone to vibrate but provides a restoring force to aide in returning the cone to an at-rest position, when the voice coil 20 is not being driven. The spider 35 typically is a circular woven cloth part with concentric corrugations. The suspension elements provide a restoring force (along the axial direction) and a centering force (along the radial direction) for the moving assembly. Single or multiple surrounds and/or spiders may be used in various transducer embodiments.
Referring now to FIGS. 2A and 3, prior art surround 50 can be seen to be a hollow semi-toroid about a center O with an inner circumferential edge 60 and an outer circumferential edge 55.
As shown in FIG. 4, surround 50 is depicted as having a semicircular or dome shaped cross-section taken along line A-A of FIG. 2A.
FIG. 3 shows a plan view of an alternative prior art surround configuration. FIG. 5 shows a circumferential section along line B-B of FIG. 3. The example surround in FIG. 3 has grooves 65 extending outward at an angle to the radial direction, over the majority of the span from the inner to the outer circumferential edges of the surround. Each groove has a V-shaped trough D at the bottom and folded corners E, F at the top.